This invention relates in general to electrical power sources for aerospace vehicles and, in particular, to an electromechanical power source for supplying electrical power on missiles.
In aerospace power systems, the evolution of electrical power source design has been influenced by the availability of an existing primary power source to drive a generator. In aircraft, electrical power has normally been derived from main engine power take-off, engine compressor bleed gas, or high velocity ram air to drive an electrical generator. In missiles, no convenient primary power source exists. Because it is impractical to bleed off motor gas, and since exoatmosphere operation eliminates ram air, batteries have necessarily been used to provide the needed electrical power for guidance, flight controls and ordnance initiation on missiles.
Within limitations, batteries have been developed to meet the present missile needs for electrical power; however, missile electrical components have been compromised to be compatible with the low voltage battery. These compromises have resulted in a dc power distribution system suitable to relatively low energy output. Low voltage dc power distribution requires large conductors and connectors to carry the high current with minimum line losses and low efficiency dc to dc voltage regulators are necessary to condition power within the using electrical components. Besides using heavier components, the inefficiency of the voltage regulators requires added weight for cooling. Also, for some components such as firing units, an inverter must be added to generate ac so that the voltage can be transformed to the higher levels.
The battery on most missiles performs adequately during flight operation because battery activation before launch allows prelaunch performance to be evaluated. A performance anomaly will cause the flight to be delayed until the battery is replaced. It is this lack of readiness, the variability of storage life, and the lack of development confidence due to aging effects that have made missile batteries troublesome.